This invention relates in general to an improved film cassette holder which includes means allowing selective portions of the film to be exposed at different times so that multiple images can be recorded on a single piece of film. The invention is primarily for use with imaging systems such as oscilloscope cameras which produce hard copies of the soft information produced on cathode ray tubes by image formation systems used primarily by physicians.
There are presently existing many imaging systems which are used to produce images on a cathode ray tube (CRT) where it is desired to produce a permanent or "hard" record of the image so produced. This is conventionally done through the use of an oscilloscope camera and the addition of suitable electronics to the oscilloscope so that a large portion of the cathode ray tube is blank while the image of interest properly sized is produced in a specific area thereof. Later images are produced in the previously blanked areas of the CRT so that multiple images are ultimately exposed on a single photographic record. As can be imagined, the electronics required to produce the image shifting, sizing and blanking are relatively complex, expensive and difficult to maintain even with the advent of modern micro-circuitry. Such complex devices must be installed by specialized service engineers and they require special calibration and involve problems of drifting from calibration. In addition CRTs have a resolution limitation inherent in their design. Therefore, no matter how optical enlargement of the CRT image is accomplished before recordation on the film, lessor resolution images as the result of sizing are the result when such is implemented. In some instances these disadvantages have been recognized and corrections attempted, usually by providing an extremely high resolution oscilloscope or other such means which needlessly increase the cost of an imaging system.
Another method commonly used to produce multiple hard images is to utilize a camera which produces one image per piece of film such as those oscilloscope cameras produced by the Polaroid Corporation. This is disadvantageous whether or not the self-developing film produced by the Polaroid Corporation is used since multiple pictures each having a separate image thereon are always more expensive than a single film having multiple images thereon of equal size to the images produced on the individual films. It should also be mentioned that in the case of self-developing films, the desired wide variety of film type is not available so that the imaging system is not as versatile as it otherwise might be.